Analyzing the BWR rod drop accident in high-burnup cores
This study was undertaken for the US Nuclear Regulatory Commission to determine the fuel enthalpy during a rod drop accident (RDA) for cores with high burnup fuel. The calculations were done with the RAMONA-4B code which models the core with 3-dimensional neutron kinetics and multiple parallel coolant channels. The calculations were done with a model for a BWR/4 with fuel bundles having burnups up to 30 GWd/t and also with a model with bundle burnups to 60 GWd/t. This paper also discusses potential sources of uncertainty in calculations with high burnup fuel. One source is the ``rim`` effect which is the extra large peaking of the power distribution at the surface of the pellet. This increases the uncertainty in reactor physics and heat conduction models that assume that the energy deposition has a less peaked spatial distribution. Two other sources of uncertainty are the result of the delayed neutron fraction decreasing with burnup and the positive moderator temperature feedback increasing with burnup. Since these effects tend to increase the severity of the event, an RDA calculation for high burnup fuel will underpredict the fuel enthalpy if the effects are not properly taken into account. Other sources of uncertainty that are important come from the initial conditions chosen for the RDA. This includes the initial control rod pattern as well as the initial thermal-hydraulic conditions.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- Nuclear Regulatory Commission, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 104426
- Report Number(s):
- BNL-NUREG-62068; CONF-9509208-1; ON: DE95016503; TRN: 95:020404
- Resource Relation:
- Conference: Specialist meeting on transient behaviour of high burnup fuel, Cadarache (France), 12-14 Sep 1995; Other Information: PBD: [1995]
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
21 NUCLEAR POWER REACTORS AND ASSOCIATED PLANTS
BWR TYPE REACTORS
REACTOR ACCIDENTS
FUEL ELEMENTS
ENTHALPY
BURNUP
COMPUTER CALCULATIONS
POWER DISTRIBUTION
EXCURSIONS
REACTOR SAFETY
CONTROL ELEMENTS
HEAT TRANSFER
HYDRAULICS
REACTOR CONTROL SYSTEMS
FEEDBACK
VOID FRACTION
CONTROL ROD WORTHS
R CODES
REACTOR KINETICS